Process and apparatus for uniformly cooling melt-spun filaments



June 2, 1964 T. R. BARNETT ETAL 3,135,811 PROCESS AND APPARATUS FORUNIFORMLY COOLING MELT-SPUN FILAMENTS Filed Nov. 13. 1961 7 1 24 I I ,201 2Z\ 4 25 3&5.

INVENTOR8 7740/1/73 ZZBJ/P/YJrr 649x040 f. Wax/vii ATTORNEYS UnitedStates Patent 3,135,811 PROCESS AND APPARATUS FOR UNIFORMLY COOLINGMELT-SPUN FILAMENTS Thomas Rosslyn Barnett and Harold Edward Warner,Harrogate, England, assignors to Imperial Chemical Industries Limited,London, England, a corporation of Great Britain Filed Nov. 13, 1961,Ser. No. 152,089 Claims priority, application Great Britain Nov. 18,1960 6 Claims. (Cl. 264-176) are cooled has a pronounced effect on theirproperties and it is generally accepted that some form of imposed quenchis required if uniformity in the cooling of filaments is to be achieved.

Known forms of quench include liquid baths or jets and flowing gases. Anexample of a gas flow quench is disclosed in British Patent 533,304 inwhich is claimed a process for the spinning of molten organicfilamentforming compositions which comprises passing a cooling mediumwith a substantially straight line flow across the spun structure whilethe latter is being transformed from the molten to the solid state. Thepreferred cooling medium is a stream of air.

The type of quench disclosed in British Patent Number 533,304, althoughwidely used by manufacturers of melt spun filaments, possesses inherentfaults which adversely affect the quality of the filaments. Thus, theflow of air passing across the curtain of extruding filaments has anon-uniform quenching effect because the air is heated in its passageover the filaments. A second disadvantage arises because the filamentsnearest to the quench outlet deflect the air stream downwards so thatsubsequent filaments are cooled at diflering distances below thespinneret.

We have found that when operating gas flow quenches, similar to thoseillustrated in British Patent 533,304, little improvement was obtainedin the variability of the filament denier compared with the use of noimposed quench, i.e. natural cooling conditions.

It is an object of our invention to provide a quenching system for meltspun filaments whereby the difficulties outlined above are very muchreduced. This and other objects and advantages will be understood fromthe following discussion and detailed description taken with thedrawings in which:

FIGURE 1 is a schematic elevational view of a meltspinning systemincluding an apparatus for directing a radial stream of quenching fluidpast the melt-spun filaments;

FIGURE 2 is a longitudinal sectional view, on an enlarged scale, of thequenching apparatus of FIGURE 1;

FIGURE 3 is a bottom view of the apparatus of FIG- URE 2; and

FIGURE 4 is a view, partly in section, taken on the line 44 of FIGURE 1.

7 According to our invention, we provide a melt spinning process of thetype wherein a molten synthetic polymer is extruded downwards through afilter pack and multi-hole spinneret or spinnerets and the filaments arecooled by a stream of gas whilst they are being stretched characterisedin that the filaments are uniformly retention when using non-circularholes.

3,135,811 Patented June}, 1964 ice cooled by a stream of gas which isdirected radially outwards from a region substantially in the centre ofthe array of filaments. Preferably the stream of gas flows horizontallyoutwards from a vertical cylindrical surface located substantially belowthe centre of a single spinneret in which the holes are symmetricallyarranged in a circle or concentric circles. It will, however, beunderstood that our invention includes the case where the filamentsemanate from a multiplicity of spinnerets, for example two spinnerets,fitted into a single pack, each providing a number of holes arranged increscent or semi-circular formation(s) so that the eventual dispositionof the filaments approximates to a cylinder or concentric cylinderswithin which the quench device is located. The preferred cooling gas isair at ordinary temperatures. By the technique of our invention severaladvantages are obtained over metheds using uni-directional flow.

One important advantage is that the mean distance between the filamentstends to increase as a result of the radial air flow, whereas in thecase of a uni-directional air stream there is often a tendency forfilaments to be blown into one another.

The air flow from a conventional cross flow unit applies a side thrustto the filaments and this is a useful property since it reduces filamentvibration which is likely to cause coalescence and denier variability.When using a radial flow system this thrust is not constant, the radialair velocity being inversely proportional to the radius. At thevelocities used the drag force exerted on the filament is approximatelyproportional to (velocity) Thus the thrust varies as 1/ (radius) and thesystem is highly damped. This is an important advantage of this flowsystem and enables filament vibration to be reduced to very low levels.

A further advantage resulting from the use of the radial outflow methodof cooling is that a more uniform treatment of the individual filamentsis obtained. A large number of holes can be accommodated, e.g. inconcentric circles, around the cooling device and suitably staggered sothat each filament receives a fresh supply of cooling gas and the gasreaching the remote filaments has not been appreciably deflected by thepreceding ones. By placing the gas source inside the filament curtain asoutlined, a more effective use is made of a given area available forspinneret holes, without having to blow gas past many filaments in arow, than by any other method.

It has been found when the source of the radial outflow gas is avertical cylinder that cylinder lengths between three and twenty inches,preferably between six and ten inches, are suitable for our purpose. Ingeneral the length of quench required increases with spun filamentdenier and the number of filaments being cooled. With up to about 50holes at spun filament deniers up to about 10 a cylinder some six inchesin length has proved adequate. For larger numbers of holes, e.g. 200 to1,000 as commonly used in the production of staple tows, or for higherfilament deniers e.g. 10 to 50 denier per filament, such as are requiredin industrial yarns a longer quench unit, preferably of at least 10inches, is desirable. The distance from the spinneret at which quenchbegins is important in that cooling must be sufliciently rapid toprevent coalescence and to ensure shape Good results are obtained with avertical cylindrical device when the cooling air first strikes thefilaments at a distance of /2 to 2 /2 from the spinneret. The rate ofgas flow required is dependent on several factors such as number offilaments, filament denier, rate of extrusion and angle of the gas flowto the filaments. In the spinning of textile and industrial yarns usinga radial outflow a polymer pump '12, a polymer filter 14, a spinneret 16gas quench substantially at right angles to the filaments a meanvelocity at the filaments between 25 and 200' feet per minute has provedsatisfactory.

We also provide a melt spinning apparatus of the type comprising ameans'foi' forwarding polymer to a melt- 5 ing zone, a pump or, pumpsfor forwarding said molten polymer to a, filter and multihole spinneretor spinnerets and a quench source, positioned centrally below thespinneret'or spinnerets to provide a uniform stream of gas around thefilaments characterised in that the quenching means comprises. a hollowporous container into which a gas is introduced under pressure.Referring to FIGURE 1 there is shown schematically a melt-spinningsystem which includes a polymer forwarding means 10,

and a yarn-collecting means 18 disposed below the spinneret 16. Aquenching apparatus 20, constructed in ac- 'cordance with the principlesof' the present invention, and receiving a stream of air through a pipe21 is disposed below the spinneret 16 at the center of a pattern ofextrusion orifices 17.

As shown in FIGURES 2 and 3,.the quenching apparatus 20 includes avertical cylinder 22 of sintered bronze sealed at thetop end with aclosure fitting 24 and provided with an inlet fitting 26 at the bottom.A solid cone-shaped rod 28, with its convergent end at the bottomextends axially along the whole length of the cylinder 22 and is securedat its ends to the fittings 24an'd 26. 'As seen in FIGURE 4 the cylinder22 is disposed along the axis of the spinneret16 so that all the fila-30 ments emerging from the orifices'17 will be swept with a radial flowof cooling air.

The construction of our quench is not restricted to sintered bronze;other porous materials 'may be used, for example, porous earthenware orperforated metal sheets or tubes. The cone-shaped inner member may alsotake other forms such as a plurality of steel mesh disks mounted on anaxial rod at substantially equal intervals, the disks increasing indiameter away from the inlet fittings of the porous cylinder. Thecontainer com- 40 -an air entry at the other.

A prising the quench need not be strictly of cylindrical section but'mayfor example be in the shape of a cone.

The process of our invention has proved of considerable value inspinning synthetic polymers including polyesters, copolyesters,polyamides, copolyamides, polyolefines and copolyolefines, In particularthe adoption of the radial outflow quench technique has greatlyfacilitated the spinning of materials having low melt viscosity such ashigh melting copolyesters of .terephthalic acid of intrinsic viscosity05 which yield filaments and fibres having useful nonepilling propertiesand enhanced dye-,atfinity. In some instances radial outflow quench hasenabled the production of filaments of low denier which could otherwisenot have been spun successfully because'of. coalescence andvariations'in filament denier. The following examples, which illustrate"but do not limit our invention, describe the spinning of typicalsyn-vthetic polymers using radial outflow quench. The gen eral spinningprocedure which provided the tubulated data involved melting the polymerby means of a screw melter and pumping metered quantities of moltenpolyiner through a sand filter and spinneret or spinnerets. The extrudedfilaments were then quenched under the conditions indicated and wound-upat the appropriate rate for the required denier. The spinnerettemperatures used were as follows:

, C. Poly(ethylene terephthalate) 280-290 Poly(ethyleneterephthalate/sebacate) 250-255 'Isotactic' polypropylene 270-280Poly(hexamethylene adipamide) 270-280 The radial outflow quench deviceinthe tabulated ex periments comprised a cylinder made of poroussinteredbronze about .1 in diameter closed at one end and having Thecylinder was placed in a vertical position in the centre of the filamentarray. at the desired distance below the spinneret or spinnerets. Acylinder of length 10" was used in all experimentsexcept numbers 4, 5, 6and 9 Where the length was 6". i

T able-Quench Experiments .Spinneret Quench 4 Denier V N P 1 Wind-51p frfier tDisfiair Melan air o. o ymer spee aance ow ve oeit Yarn 'ro ertesNo. of Hole shape and Hole arrangement (ftz/miu.) ment Type from rate,at filap p 1 j 7 holes size sptucu. ft./ merits,

neret, min. ftJmin.

inch (a) (1') v 1 Polyethylene 508 Round, 0.009 Equally'in 4 con- 2, 7005 Radial 1 60 65 Denier O.V.

terephthalate' dia. centric circles, outflow 10%; (intrinsic vismeandiameter Cross flow. 1 60 65 20%. cosity 0.67). 4.0. 21%. 2 do 336 doEqually in 3 eon- 1,800 10 Radial 1 40 8%.

. centric circles, outflow mean diameter do 1 1 100 110 6%. 4.1". Cross1 40 45 18%;

. flow I 18 3 do 981 Round, 0.008 Equally in 9 con- 1, 830 5 Radial 115%;. vdia. centric circles, V outflow.

mse an diameter Would not spin. 4.1;. do '36 Round, 0.009 In one circle.3, 800 7 do-- %-2% 12 50 O.V. 1.0-1 .4%.

' p dia. diameter 2". 2.0%. 5 do 36 Y shaped arm, do 4,000 7. Radial 1 625 1.2%. p length 0.02; outflow width, 0.005. V O. 1% 12 50 1.2%. p 3.3.6 do 24 Round, 0.02 do 4,000 7 Radial 1 12 50 0.9g; V dia. a I 7 outflow1.9 7; Polyethylene 508 Round, 0.009 Equally in 4 con- 2, 200 5 Radial1% 50 55 8%? terephthalate dia. centric circles, outflow (intrinsicvismean diameter 18%. cosity 0.60). a p 4.0. V 8--.; do 250 cr ciform.Eq lly in 5 con- 2, 200 10 Radial 1% Shape factor '0.035/0.004. Icentrie circles, outflow O.V. 5%; j

. mean diameter 7 Cross section i 3.75. lderu'er O.V.

15%. Shape factor Denier C V 6 Table-Continued Spinneret Quench DenierWind-up per Dis- Air Mean air No. Polymer speed fllatance flow velocityYarn properties No. 0! Hole shape and Hole arrangement (it/min.) mentType from rate, at filaholes size spincu. ft./ ments, neret, min.ItJmin.

inch

9 Polyethylene 2 x 48 Round, 0.009 In twin packs. 4,300 7 Radial 1 18Denier C V terephthalate dia. Each spinneret outflow. 1.1%. (intrinsicviscontains three 3.0%. cosity 0.60). rows of holes in crescentformation. Mean distance from centre, 1.1".

10.-- Ethylene ter- 448 Round, 0.009 Equally in 4 con- 2, 700 5 Radial 18%.

ephthalate/ dia. centric circles, outflow. sebacate 94:6 mean diameterWould not spin copolymer 4.0. due to coales- (intrinsic viscence. cosity0.47).

11 do 252 do Equally in 3 con- 2, 700 10 Radial y -2y 18%.

centric circles, outflow. ing a n diameter Would not spin. 12-.. do 238Y shaped arm, In 4 circles, mean 2, 200 10 Radial 1 10% (triangularlength 0.015; diameter 3.6. outflow. flls. width 0.0045. 10% (shapevariable). 13 clo 250 Oruciiorm In 5 concentric 2, 200 8 Radial 2% 70 85Denier G.V. 9%

0.035/0.004. circles, mean outflow. (circular yarn).

diameter 3.75.

14- lsotactic poly- 85 Round, 0.015 In 2 circles mean 1, 000 50 Radial1% 6%.

propylene dia. diameter 3.6. outflow. (melt index 13% (some coal- 23.2g.). escence). 15 d 85 --do -do 1,000 37 Radial 1% 40 50 2.5%.

1 outflow.

16. 05 nylon (rela- 508 Round, 0.009" Equally 1n 4 con- 2, 200 5 DenierO.V.

tive viscosity dia. centric circles, 15%.

34.). inggn diameter 27%.

17-.. do 252 do Equally in 4 con- 1,800 10 Radial 1% 30 35 11%.

centric circles, outflow. mean diameter 22%. 3.6.

l8 66 nylon (rela- 36 Round, 0.013 One circle clia- 2,800 7 5 Radial 113 55 0.8%.

tive viscosity dia. meter outflow. 7

Norns:

(1) The quench distances from spinneret quoted are those distances belowthe spinneret at which air first came into contact with the filaments.(2) The air flow rate is the total volume of gas per unit of timepassing through the quench device.

(3) Coeflicients of variation (C.V.) are percentage estimates of theaverage range of denier and shape factor respectively.

(-1) Intrinsic viscosity measurements were made at 8% (wt.)concentration in ortho-chlorophenol at 25 C.

(5) The relative viscosity of 66 nylon was measured at 8.4% (wt.)concentration in 90% formic acid at 25 C.

(6) The melt index of isotactic polypropylene is the amount in gramsextruded in 10 minutes at 0. through orifice 0.08 25" in diameter and0.316 long under a load oi 10 kgrn.

What we claim is:

l. A melt-spinning process of the type wherein a molten syntheticpolymer is extruded downwards through a filter pack and at least onemultihole spinneret and wound upon a yarn collecting means characterizedin that the filaments are uniformly cooled by a stream of gas which isdirected radially outwards from a vertical cylindrical surface locatedsubstantially in the center of an array of filaments emanating from thespinneret and at a distance from the spinncrct such that the cooling gasfirst contacts the filament at a distance between 0.5 and 2.5 inchesfrom the spinneret.

2. A melt-spinning process according to claim 17 wherein the cooling gasis distributed with a mean velocity of 25-200 feet per minute from ahollow porous cylinder closed at one end and having an inlet for thecooling gas at the other end.

3. A melt-spinning process according to claim 2 wherein the hollowcylinder is fitted inside with a tapered metal cone increasing indiameter away from the gas inlet.

4. A melt-spinning process according to claim 1 wherein the denier perfilament of the spun filaments as collected is between 5 and 50.

5. A melt-spinning head having means defining a plurality of downwardlyfacing spinning orifices, said orifices 50 being disposed in a generallycircular pattern; a vertically 55 cylinder being sealed at the top andprovided with a gas inlet at the bottom; a tapered solid cone withinsaid cylinder and extending along a substantial length thereof, saidcone increasing in diameter away from the gas inlet; and means fordelivering cooling gas to the gas inlet.

60 6. Apparatus as in claim 5 wherein said cylinder is constructed ofsintered bronze and is between 3 and 20 inches in length.

References Cited in the file of this patent 65 UNITED STATES PATENTS2,730,758 Morrell ct al. Jan. 17, 1956 FOREIGN PATENTS 572,083 CanadaMar. 10, 1959

1. A MELT-SPINNING PROCESS OF THE TYPE WHEREIN A MOLTEN SYNTHETICPOLYMER IS EXTRUDED DOWNWARDS THROUGH A FILTER PACK AND AT LEAST ONEMULTIHOLE SPINNERET AND WOUND UPON A YARN COLLECTING MEANS CHARACTERIZEDIN THAT THE FILAMENTS ARE UNIFORMLY COOLED BY A STREAM OF GAS WHICH ISDIRECTED RADIALLY OUTWARDS FROM A VERTICAL CYLINDRICAL SURFACE LOCATEDSUBSDTANTIALLY IN THE CENTER OF AN ARRAY OF FILAMENTS EMANATING FROM THESPINNERET AND AT A DISTANCE FROM